Figure 17. Field occurrences and hand specimens of Microfacies 4 sinter. (1) Thin siliceous sinter rims (orange colour, red arrow) forming on small pumice clasts that rest on fine sandy substrates. Coin in the centre of photo is 2 cm wide. Bar represents ~15 cm. (2) Close-up showing underlying sandy substrate (covered by green microbial mat) that is protected from erosion by the overlying orange sinter, thereby forming pillar-like structures. Bar represents 4 cm. (3) Small hole dug into the sandy substrate revealing warm (45°C) thermal pore water at shallow depths. Shovel to the upper right is 15 cm wide. (4) Vertical section through a thin siliceous rim sinter. Pumice clast underneath sinter is covered with green microbial mat. Red arrow indicates thin internal laminae that are convex in shape. Bar represents 0.8 cm.